elk/utils/language.ts

export function matchLanguages(languages: string[], acceptLanguages: readonly string[]): string | null {
  {
    // const lang = acceptLanguages.map(userLang => languages.find(lang => lang.startsWith(userLang))).filter(v => !!v)[0]
    // TODO: Support es-419, remove this code if we include spanish country variants
    const lang = acceptLanguages.map(userLang => languages.find((currentLang) => {
      if (currentLang === userLang)
        return currentLang

      // Edge browser: case for ca-valencia
      if (currentLang === 'ca-valencia' && userLang === 'ca-Es-VALENCIA')
        return currentLang

      if (userLang.startsWith('es-') && userLang !== 'es-ES' && currentLang === 'es-419')
        return currentLang

      return currentLang.startsWith(userLang) ? currentLang : undefined
    })).filter(v => !!v)?.[0]
    if (lang)
      return lang
  }

  const lang = acceptLanguages.map((userLang) => {
    userLang = userLang.split('-')[0]!
    return languages.find(lang => lang.startsWith(userLang))
  }).filter(v => !!v)[0]
  if (lang)
    return lang

  return null
}